Brightening plastics with 2-aryl-5-cyanonaphthoxazole brighteners

ABSTRACT

Translucent plastics, particularly polyvinyl chloride, cellulose acetate, and polyolefins such as polyethylene are brightened by distributing uniformly therethrough about 0.01 to 0.5 percent by weight of a 2-aryl-5-cyanonaphthoxazole wherein the 2-aryl moiety is naphthyl, styrylphenyl, anisoylaminophenyl, carboxybenzoylaminophenyl, phenylureidophenyl or acylaminophenyl in which the acyl group is the residue of a higher fatty acid.

United States Patent Buell [451 May 2, 1972 [54] BRIGHTENING PLASTICS WITH 2- ARYL-S-CYANONAPHTHOXAZOLE BRIGHTENERS [72] Inventor: Bennett George Buell, Bound Brook, NJ.

[73] Assignee: American Cyanamld Company, Stamford,

Conn.

[22] Filed: Apr. 13, 1970 [21] Appl. N0.: 28,146

[52] US. Cl. ..106/176, 252/3012 W, 260/45.8 NZ, I 260/307 D [51] Int. Cl ..C08b 27/68, C08f 45/67 [58] Field of Search ..260/45.8 N2, 307 D; 106/176; 252/3012 W [56] References Cited UNITED STATES PATENTS 3,336,330 8/1967 Sc'hinzeletal ..260/307 3,167,565 l /l965 Buell ..260/307 3,449,333 6/1969 Dorlars et al. 3,526,768 9/1970 Rai et al ..250/71 Primary Examiner-M. J. Welsh Assistant Examiner-R. A. White Attorney-John L. Sullivan [5 7] ABSTRACT 3 Claims, N0 Drawings BRIGHTENING PLASTICS WITH 2-ARYL-5- CYANONAPHTHOXAZOLE BRIGHTENERS This invention relates to the brightening of translucent plastics such as polyvinyl chlorides, nitrocellulose, cellulose acetate and triacetate, nylons, poly(methyl methacrylate) and polyolefins, such as polyethylene, polypropylene, polystyrene and the like. It is based on the discovery that such plastics can be brightened by distributing throughout the substance thereof, in brightening quantities, a 2-aryl-5-cyanonaphthoxazole brightener of the type hereinafter described. The invention includes the brightened plastics themselves, methods wherein they are brightened by incorporating one or more of these compounds therein, and also certain 2-aryl-5- cyanonaphthoxazoles as new chemical compounds.

The brightening of textile fibers and fabrics by applying optical brightening or whitening agents to the surfaces thereof is well known, and several entire classes of brightening agents are known to be effective for this purpose. The brightening of plastics intended for molding, casting or extrusion into relatively thick pieces or sections presents, however, an essentially different problem, for the brightening agents are distributed more or less uniformly throughout the substance of these plastics instead of being located on their surfaces. They brighten the plastics by fluorescing after absorption of light in the ultra-violet wavelengths, and the visual appearance of the brightened plastic is therefore influenced by such factors as the particular wavelength of fluorescence of the added brightener, the color and nature of the plastic substrate in which it is incorporated, and also the compatibility and affinity of the brightener with and for the particular plastic. These brighteners have stability to heat, and particularly to light when incorporated into the plastic.

It is evident, therefore, that the usefulness of a compound as a brightener for a translucent plastic cannot be predicted on the basis of its chemical structurealone. On the contrary, each compound must be evaluated individually on the basis of its behavior in individual plastics with particular reference to the extent and color of its fluorescence in sunlight and the other factors discussed above.

l have found that all of these requirements are fulfilled by certain 2 -arylnaphthoxazoles when they contain a cyano-substituent in their 5 position. Polyvinyl chloride in which small quantities of these materials are distributed uniformly is both brighter and appears to be more clear than a control sample containing no brightener. Polyolefins such as polyethylene and polypropylene are much brighter, and other translucent plastics such as nitrocellulose, cellulose acetate and triacetate, nylons and poly(methyl methacrylate) are likewise improved. These results are obtained when the brightening compounds are present in quantities within the range of about 0.01 to 0.5 percent and preferably 0.02 to 0.1 percent based on the weight of the plastic, which quantities are sometimes hereinafter described as brightening amounts. Larger quantities could of course be used, but do not ordinarily give any further improvement.

The 2-aryl-S-cyanonaphthoxazoles of my invention are compounds of the formula in which A is one member of the group consisting of oxygen linked singly to the oxazole carbon atom C and nitrogen bonded doubly to the same carbon atom and B is the other member of this group. I have found that the above-described brightening properties are possessed by the compounds of this class wherein the aryl moiety is naphthyl, styrylphenyl, anisoylaminophenyl, carboxy-benzoylaminophenyl, phenylureidophenyl or acylaminophenyl in which the acyl group is the residue of a higher fatty acid, preferably of about 12-18 carbon atoms such as lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid and the like. Some of these compounds, notably the 2-anisoylaminophenyl-5-cyanonaphthoxazoles and the Z-naphthyl-S-cyanonaphthoxazoles are new chemical compounds, and therefore their properties and their methods of preparation are described in detail in the following exampics.

The brighteners of my invention are prepared from 4- cyanoaminonaphthols. When a l-amino-4-cyano-2-naphthol is used the naphthoxazole is of the 1,2-d type, whereas the 2,]- d naphthoxazoles are obtained from 2-amino-4-cyano-l naphthol. The two types are equally good brighteners, and therefore both are included within the scope of my invention.

In preparing the brighteners, the cyanoaminonaphthol is reacted with an appropriately substituted aroyl chloride to form an amide, which is ring-closed by pyrolysis or by fusion with acid agents such as boric acid to form the naphthoxazole. This can then be further reacted if necessary, as by the reduction of nitro groups to amines, acylation and the like, in order to complete the formation of one of the above-described 2- aryl substituents.

Ordinarily the amide-forming reaction is carried out at an elevated temperature and in an organic medium such as pyridine, chlorobenzene, dichlorobenzene or acetone. Temperatures may vary between 50C. and reflux.' The intermediate product is obtained as an insoluble precipitate or, when the solvent is water-miscible, by drowning the reaction product inwater. The ring-closing reaction to give the oxazole is conducted at elevated temperatures by direct heating without a solvent or by fusing with acid agents such as boric acid, paratoluene sulfonic acids, polyphosphoric acid and the like. The product is preferably purified by such methods as recrystallization from methoxyethanol or by chromatography.

The brighteners so obtained are usually/incorporated into the plastics while the latter are in a melted or plastic state. Thus the brightener in finely divided form may be worked into the plastic on heated rolls by the procedures described in Example l.

My new brighteners shown a strong fluorescence under ultra-violet light after incorporation into plastics. For this reason they strongly brighten polyvinyl chloride, polyethylene, cellulose acetate and the other plastics enumerated above. in polyvinyl chloride and in polyethylene especially they have excellent light fastness, which is in many cases superior to known brighteners. For example, the 2-( panisoylaminophenol)-5-cyanonaphthoxazole of Example I is twice as fast to light as a commercial styryl benzoxazole brightener in polyvinyl chloride.

The fluorescent hue of these brighteners is a true blue fluorescence when they are uniformly incorporated into translucent or transparent plastics in the brightening quantities described above. In many cases they make a clear plastic appear clearer still; the reason forthis is unknown, but it is an added advantage of these embodiments of the invention.

The invention will be further described and illustrated by the following specific examples, wherein the special affinities of individual compounds for specific plastics or polymeric substrates are noted together with the preparation and properties of the compound. It will be understood, however, that the invention in its broader aspects is not limited to these examples.

EXAMPLE 1 O NHCO OCH.

heated with stirring to 255C. When cyclization is complete,

the melt is cooled and taken up in 500 ml. of methoxyethanol. The mixture is boiled, cooled and the product filtered, washed with alcohol and dried in vacuo. The yield of -cyano2-(pnitrophenyl-naphth[2,2,d]oxazole,product B. is 17.3 .g. It should be noted that the position 4 in the naphthol becomes position 5 in the naphthoxazole. I

Reduction of the nitro oxazole B to the corresponding amino oxazole C is carried out in a mixed solvent of 500 ml. methoxyethanol and 500 ml. alcohol, at 80C., by adding 16 g. of sodium sulthydrate in 40 ml. of water. When the reaction is complete, the solution of the product is clarified by treatment with activated charcoal and filtration. The amino product, C,". in the filtrate is. precipitated by water. It is filtered, washed with alcohol and dried. Yield is 12.63 g of 2-(paminophenyl)-5-cyanonaphth[l,2-d]oxazole,' product C." Recrystallization from monochlorobenzene with activated charcoal gives 9.20 grams m.p., 275-278C. The product C exhibits a blue-green fluorescence in alcohol.

.Acylation of the above amino oxazole, product C," is effected-by mixing 7.6 g. of that product in 500 ml. pyridine with 5.6 g. of p-anisoyl chloride. The solution is heated on a steam bath for one hour and then cooled. Water, is added to precipitate the product. The product is filtered washed with water and dried. Yield is 10.29 g. crude of 2-(panisoylaminophenyl)-5-cyanonaphth[ 1,2-d1oxazole.

Theproduct is recrystallized fromortho dichloro-benzene after clarifying in the presence of activated charcoal and then from 900 ml. of methoxyethanol and dried to give 8.40 g. m.p.

2835C. It is dissolved in 250 ml. of hot dirnethylformamide,

a few ml. of formaldehyde added, and diluted with 200 ml. of

ethanoL-After standing,the product is filtered, washed with ethanol and dried. Yield 7.00 g. m.p. 2804C. 2-(panisoylaminophenyl)-5-cyanonaphth[1,2-d]oxazole. A 360. mu.

V If, in the foregoing preparation, an equal quantity of 2- amino-4-cyano-l-naphthol is substituted in the first step, the 2-(p-nitrobenzoylamino)-4-cyano-l-naphthol, product A, is obtained in the same yield. When this is carried through the remaining steps of the process the product is 2-(panisoylaminophenyl )-5-cyanonaphth[ 2, 1 -d ]oxazole.

These compounds are strong brighteners of polyvinyl chloride plastics and the brightened plastics have superior lightfastness. They may be incorporated uniformly into polyvinyl chloride or other plastic by the following procedure.

A steam heated 2-roll Thropp-mill one roll at 320F. and the other roll at 275F. is used formixing a compound of this example -with the plastic. One hundred grams of polyvinyl chloride powder is placed in the nip and banded. When a workable molten mass is obtained, 20 milligrams of the oxazole compound is added. The band is cut at every pass for 50 passes. It is then transferred to a molding machine and molded at 320F. into a sheet or film of 20 mils.

The film containing the oxazole compound is much brighter than a blank film similarly derived. Under ultra-violet light it shows a strong blue fluorescence.

When exposed to a fluorescent sun lamp, the brightened film holds up 100 hours before a break occurs. It is twice as fast to light as a styrylbenzoxazole brightener similarly incorporated in polyvinyl chloride.

EXAMPLE 2 To 1.42 g. (0.005 mole) of 1 Z-(p-aminophenyD-S- cyanonaphth[l,2-d]oxazole (product C" of Example 1) is added 0.6 ml. (0.005 mole) phenylisocyanate. The mixture is heated on a steam bath until the reaction is complete. Hot alcohol is added. The product isvfiltered. It is recrystallized from methoxyethanol to give 1 g. product m.p. 2l3-215C. It is recrystallized from monochlorobenzene and then from a methoxyethanol-ethanol mixture to give 0.17 g. m.p. above 350C. A,,,,,,=363 my" v y This compound, which is 2-(p-phenylureidophenyl)-5- cyanonaphth[1,2-d]oxazole, brightens polyvinyl chloride strongly when incorporated therein in amounts offrom about 0.02 to 0.1 percent on the weight of the plastic'by the procedure described in Example 1 and has good fastness to light. It also brightens nylon.

' EXAMPLE 3 JOOH To 20 ml. of pyridine is added 2.84 g. (0.01 mole) of 2-(p- .aminophenyl)-5-cyanonaphth[1,2-d]oxazo1e prepared as in Example 1, C (an intermediate) and 1.48 g. (0.01 mole) of phthalic anhydride. The mixture is boiled and then set on a steam bath for 1 hour. It is poured into cold water and filtered. The product is taken up in 250 ml. of ethanol and made a1- kaline with 5N sodium hydroxide. The resultant sodium salt of the oxazole is separated and dissolved in 200 ml. alcoholand 50 ml. water. After heating to dissolve and treating with activated charcoal, the solution is clarified by filtration and then acidified with 5N hydrochloric acid. The product is filtered, washed with alcohol and water and dried in vacuo. Yield is 1.39 g. The m.p. is higher than 303C. The ultra-violet spectrum shows A,,,,,,= 370 mu. 7

This compound, which is 2(p-carboxybenzoylaminophenyl)-5-cyanonaphth[l,2-d]oxazole, brightens both polyvinyl chloride and polyethylene when incorporated therein in -amounts of about 0.05-0.l percent by weight by the The compounds also brighten polyethylene, polystyrene,

procedure of Example 1. It is fast to light for the full life of the brightened plastic.

EXAMPLE 4 To 25 ml. pyridine is added 1.00 g. (0.0035 mole) of product C of Example 1 and 1.18 g. (0.0039 mole) of stearoyl chloride. The whole is heated to the boil and cooled. It is drowned in ice water and the product filtered and dried. Recrystallization from monochlorobenzene gives 1.22 g. crude product m.p. 168-184C. This is chromatographed from chloroform on alumina and again recrystallized from monochlorobenzene to give 0.59 g. m.p. 186C., of 2(pstearoylaminophenyl)-5-cyanonaphth[1,2-d]oxazole A 355 mp.

compound brightens polyvinyl chloride, in which it shows good lightfastness. It also brightens polyethylene.

EXAMPLE 5 .azole. This is cooled, taken up in methoxyethanol, treated with activated charcoal, filtered and reprecipitated with water, and collected and dried.

The 2-(p-styrylphenyl)-5-cyanonaphth[l,2-dloxazole so obtained is further purified by recrystallizing from methoxyethanol and water. It then melts at 248249C.; its ultraviolet absorptivity A is at 375 mu.

This compound brightens polyvinyl chloride, giving a slightly greenish blue effect of good lightfastness when incorporated in amounts of about 0.02-0.06 percent by weight. It gives a similar effect in cellulose acetate and also in polyethylene. A representative procedure for incorporating it into the latter is as follows.

A steam heated two-roll Thropp-mill one roll at 250F. and the other roll at 100C. is used for mixing. One hundred grams of polyethylene beads are placed in the nip and banded. Twenty milligrams of the compound is added to the banded polyethylene. The band is cut at every pass for passes. lt is then molded under pressure at 280F. into a 20 mil sheet.

Appearance of the sheet is much whiter than an untreated sheet. In polyethylene it is superior in brightness to the known brighteners such as a 2-styrylbenzoxazole brightener.

This compound has special affinity for polyester textile fibers when applied from acid bath in the presence of a carrier. It imparts a slightly greenish blue fluorescence. Since the commercial ethylene-bis-benzoxazole brighteners in current use for polyester tend to be too red, this more greenish blue fluorescence has merit.

The brightener also has strong affinity for nylon, producing a greenish blue fluorescence.

EXAMPLE 6 To 50 ml. thionyl chloride is added 3.44 g. (0.02 mole) of lnaphthoic acid. When conversion to the acid chloride is complete it is isolated then 3.68 g. of l-amino-4-cyano-2- naphthol in 50 ml. pyridine is added. The whole is refluxed two hours, then drowned in water. The pyridine is neutralized with 5N hydrochloric acid. The product precipitates, is filtered and dried. it is then fused with l g. of boric acid at 2509C. for 20 minutes. The product is recrystallized from methoxyethanol. It is chromatographed in chloroform through alumina using chloroform as eluant. The chloroform is stripped off and the product recrystallized from methoxyethanol and activated charcoal. The product obtained is 2- (l-naphthyl)-5-cyanonaphth[l,2-d]oxazole mp. 239C. A is 365 mu.

lt brightens polyvinyl-chloride and shows good fastness to light. Film containing this compound appears more clear than film without it. It also brightens polyester fibers when applied with a carrier in aqueous bath.

EXAMPLE 7 in the procedure of Example 6 if an identical amount of 2- naphthoic acid is used instead of l-naphthoic acid and the rest of the rocedure kept the same, the roduct obtained is mp. 253C.

A is 355 mp.

lt brightens polyvinylchloride, causing it to appear very slightly clearer and is of good fastness in this plastic.

What I claim is:

l. A brightened plastic of the group consisting of polyvinyl chloride and polyolefin plastics having uniformly distributed therethrough about 0.01 to 0.5 percent by weight of a 2-aryl- S-cyanonaphthoxazole wherein the 2-aryl moiety is a member of the group consisting of naphthyl, styrylphenyl, anisoylaminophenyl, carboxybenzoylaminophenyl, phenylureidophenyl' and acylaminophenyl in which the acyl group is a higher fatty acid residue.

2. A brightened plastic of the group consisting of polyvinyl chloride, cellulose acetate and polyethylene having uniformly distributed therethrough about 0.01 to 0.5 percent by weight of a 2-aryl-5-cyanonaphthoxazole of the group consisting of 2- (p-anisoylaminophenyD-S-cyanonaphthoxazole and 2-(pstyrylphenyl)-5-cyanonaphthoxazole.

3. A brightened plastic according to claim 1 wherein the 2- aryl-S-cyanonaphthoxazole is a Z-naphthyl-S-cyanonaphthoxazole. 

2. A brightened plastic of the group consisting of polyvinyl chloride, cellulose acetate and polyethylene having uniformly distributed therethrough about 0.01 to 0.5 percent by weight of a 2-aryl-5-cyanonaphthoxazole of the group consisting of 2-(p-anisoylaminophenyl)-5-cyanonaphthoxazole and 2-(p-styrylphenyl)-5-cyanonaphthoxazole.
 3. A brightened plastic according to claim 1 wherein the 2-aryl-5-cyanonaphthoxazole is a 2-naphthyl-5-cyanonaphth-oxazole. 